Why do we practice Buddhism? To gain enlightenment, or find out the meaning of life? The practice of Buddhism goes far beyond that.
What I mean by "practicing without ego" is to let go of any notion of ourselves. Our nature as humans is to expect rewards for our practices of compassion, devotion, and giving. By expecting rewards, we are practicing with our ego and not the Dharma. We always want something, which is why desire is described as a holy truth. When we desire rewards or enlightenment, we only end up with more suffering because these are not given to us.
By practicing selflessly, and not being attached to the outcome, we can realize a feeling of liberation. It's okay to feel good about helping others and devoting yourself, but in reality these feelings are truly empty. Just practice and let go. What comes along, comes along. It's not always true that "what goes around, comes around." Sometimes what goes around, never comes back. Sometimes it comes back in a way opposite of what we wanted. Want stems from desire, stemming from attatchment, stemming from ego (which leads to disappointment and suffering).
Do not expect anything, and let go of the ego.
When you seek it, you cannot find it. -Zen proverb.